1. Field of the Invention
This invention relates to open cycle, ocean thermal energy conversion systems, and more particularly, to an axial flow turbine apparatus having an outer casing which simultaneously functions as a water carrying conduit and structural support.
2. Description of the Prior Art
Ocean thermal energy conversion is a process by which the normal temperature difference existing between relatively warm surface waters and relatively cold, subsurface waters is utilized to develop a pressure difference across a turbine through which a motive fluid is expanded. The surface of large water bodies, such as oceans, acts as a large, cheap solar energy collector. The expansion energy of the motive fluid passing through the turbine causes the turbine's rotor to spin which, in turn, drives a generator. Due to the small temperature and pressure differences typically found in ocean thermal energy conversion cycles, the efficiencies are rather low. Since, however, the cost of operation for an ocean thermal energy conversion system is substantially zero, since no fuel is consumed to produce the top cycle temperature, the primary limiting construction there is the capital cost of the equipment components. Components such as the turbine and heat exchangers must by necessity, be very large to yield reasonable net electrical power output.
Ocean thermal energy conversion systems are typically classified to be of the open and closed cycle variety in which seawater and other volatile fluids are respectively utilized for the motive fluid which is expandable through the turbine. While the cycle varieties each have certain advantages over the other, a primary disadvantage of the open cycle OTEC has been the extremely large floating platform or hull structure required to support the power generation equipment and the high cost for materials and construction thereof. Reduction in the size and cost of the large platforms required for open cycle OTEC power systems could provide a favorable advantage for such open cycles with closed cycle OTEC systems. Conventional axial flow turbines typically include horizontally disposed shafts and associated casing structures which require support foundations of substantial dimensions. Platform size reduction, however, necessitates an unconventional turbine which utilizes minimum platform space and functionally cooperates with other OTEC equipment in a spacially efficient manner.